1. Field of the Invention
The present invention relates to a method for producing an inflatable balloon catheter which has an inflatable catheter tip and a double lumen catheter shaft joined together in such a manner that a smooth, continuous, outer surface results at their outer juncture.
Inflatable balloon catheters, also known as "Foley catheters," generally are used to drain fluid from or inject fluid into an internal body cavity, for example, the urinary bladder. Such catheters are inserted into the body cavity through an incision or a natural opening, for example, the urethra which leads to the urinary bladder.
Inflatable balloon catheters usually include a flexible, resilient, tubular shaft having two or more passages or lumina extending axially through it. An inflatable balloon is attached at the distal end of the shaft and communicates with one lumen called the inflation lumen. Sterilized, pressurized fluid is pumped through the inflation lumen to inflate the balloon when it is positioned inside the body cavity to be catheterized. The enlarged balloon acts to hold the catheter in position, preventing its disengagement from the cavity.
A second lumen, called the drainage lumen which terminates in one or more drainage eyes, opens into the body cavity so that undesirable fluids can be drained from or medicinal fluids introduced into the cavity.
When it becomes necessary to remove the catheter, the balloon is deflated and the catheter is withdrawn.
To minimize tissue irritation during insertion, operation, and withdrawal of the catheter, both the catheter shaft and balloon tip should be made of an inert, flexible material such as silicone rubber and should be smooth, rounded, and have outside diameter as small as possible yet be large enough to adequatedly perform the drainage function. That is, the catheter shaft should have sufficiently large diameter to permit the relatively thick-walled construction required to prevent its collapse and to permit the drainage lumen to have inside diameter sufficiently large to minimize chances of occlusion by crystallization of the fluid being drained. The tip should also be rounded so that it may be introduced through the body opening with minimum discomfort. Moreover, the tip should be joined to the catheter shaft to form a smooth, continuous outer junction that itself will not cause irritation, discomfort, or pain. In particular, the balloon tip and shaft should be joined in a way that does not result in a shoulder, rib or, rough trimmed edges at the outer juncture.